By: T. Berry Brazelton, M.D., and Joshua Sparrow, M.D.

Q. My older daughter was conceived through IVF (in vitro fertilization). Shortly after her birth I began wondering when she might ask the inevitable question, “Where did I come from?” What would you say?

A. Children usually ask that question at age 4 or 5 when they begin to wonder about the differences between boys and girls’ bodies, and between their bodies and their parents’. This curiosity coincides with the time when children deeply want to imitate their parents and identify with them. They are becoming more aware of gender differences and seek to understand why they are different and how their bodies work.

The questions are perfectly natural: “Where did I come from?”, “How does the seed get to the egg?” and “How does the baby get out?”

So it’s a good idea to be ready when your child is approaching that age. Conception, pregnancy and birth are such miraculous feats that it is hard for any of us to fathom just how they all could happen. Add in the marvels of medical technology and it’s no wonder we struggle to answer children’s questions.

Fortunately, children only take in simple, clear answers aimed at their level of understanding. If you overshoot with details, eyes glaze over or the kids start fidgeting and change the subject.

Your reply to your child depends on a few specifics – including her age and her interest in bodies or babies. Your reply also depends on whether she was conceived with her mother’s egg or a donor’s.

The basic information is the same. Babies come from an egg from a woman and a kind of seed called sperm from a man that fertilizes the egg. These facts of life are already surprising and hard enough for a child to understand. You may not be adding much to spell out that sometimes the egg comes from the mommy and the sperm from the daddy, and sometimes they get it from another woman or another man if they need it to make the baby they both want so much to have.

By now, the child may have heard enough until the next conversation. If so, you can save this information for then: The fertilized egg grows inside the woman’s body, in her womb – a kind of pouch inside made especially for babies to grow in. The baby comes out through the mother’s birth canal, or she may need an operation to help the baby come out.

Parents love their children no matter where they come from, how they are conceived and born, or what the connection happens to be between biological parents and “real” parents in a family. This is what children need to know most of all.

For more information to answer children’s questions about their bodies, see Robie H. Harris’ books, including “It’s Perfectly Normal.”

How to talk about the birds and the bees? Tell the truth. If not, you may lose a child’s trust. You needn’t tell the whole truth all at once, just what the child can handle. Be open to a child’s questions and ready to answer, which will prepare the way for open communication all the way through adolescence. Let the child’s questions and behavior guide you. If you watch and listen you’ll know when you’ve given a little too much information.

Responses to questions are not intended to constitute or to take the place of medical or psychiatric evaluation, diagnosis or treatment. If you have a question about your child’s health or well-being, consult your child’s health-care provider.

Dr. Brazelton, prior to his passing, was the founder and head of the Brazelton Touchpoints Center, which promotes and supports community initiatives that are collaborative, strength-based, prevention-focused sources of support for families raising children in our increasingly stressful world. Dr. Sparrow, a child psychiatrist, is currently the Director of the Brazelton Touchpoints Center. Learn more about the Center at www.touchpoints.org.

Reprinted with permission from the authors.